This invention relates to an infrared and ultraviolet ray absorbing glass which retains sufficiently high visible transmittance and can easily be produced by the conventional float process and can easily be tempered by the conventional air quenching method. The glass has a greenish tint and is particularly suitable for use in building and vehicle windows.
For windows of buildings and automobiles and other vehicles, there is an increasing demand for sheet glass that is sufficiently transparent to visible light and possesses the capability to absorb not only infrared rays but also ultraviolet rays. The absorption of infrared radiation in window glasses offers comfort to the occupants or contributes to the saving of energy by reducing the air conditioning load, and the absorption of ultraviolet rays serves for the purpose of improving habitability of the rooms or vehicle cabins and preventing discoloration or deterioration of the interior or onboard articles made of organic materials.
One measure for reducing the transmittance of infrared and/or ultraviolet rays through a glass is to provide the glass with a reflective and/or absorptive coating. However, in many cases it is more desirable to render the glass itself absorptive of infrared and ultraviolet rays by modifying the glass composition. From an industrial point of view it is desired that an infrared and ultraviolet absorbing glass can be produced by a conventional method, and particularly by the conventional float process, without significantly changing the particulars of operations. Also it is desired that an infrared and ultraviolet absorbing glass can easily be toughened by a conventional tempering method.
it is known to render a soda-lime-silica glass absorptive of infrared radiation by incorporating iron in the glass Although ferrous iron Fe.sup.2+ (expressed as FeO) is particularly effective for infrared absorption, it is usual to produce a glass containing both ferrous iron and ferric iron Fe.sup.3+ (expressed as Fe.sub.2 O.sub.3) because if FeO alone is present in a relatively large amount the visible transmittance of the glass and the tint of the glass are unfavorably affected. In practice Fe.sub.2 O.sub.3 is used as a raw material, and an adequate portion of Fe.sub.2 O.sub.3 is reduced to FeO during the glassmaking process.
Also it is known to incorporate cerium oxide CeO.sub.2 and/or titanium oxide TiO.sub.2 in a soda-lime-silica glass to render the glass absorptive of ultraviolet rays.
U.S. Pat. No. 4,792,536 shows an infrared absorbing glass, which can be rendered absorptive of ultraviolet radiation too, and a method of producing same. Basically the glass is a soda-lime-silica glass, and in the glass the content of iron expressed as Fe.sub.2 O.sub.3 is 0-1 wt %, and preferably 0.45-0.65 wt %, and at least 35% of the total iron is in the ferrous state as FeO. Besides, the glass contains 0-1.5 wt % of at least one of CeO.sub.2, TiO.sub.2, V.sub.2 O.sub.5 and MoO.sub.3, preferably including 0.25-0.50 wt % of CeO.sub.2. An important feature of the glass of this patent is that the residual SO.sub.3 content is less than 0.02 wt %.
From an industrial point of view the proposal of U.S. Pat. No. 4,792,536 is not favorable because the proposed infrared and ultraviolet absorbing glass cannot be produced by the conventional melting operations in the float process. As is disclosed in the patent specification, due to the very low content of sulfur it is necessary to employ complicated two-stage melting and refining operations by using a special stirring means.
U.S. Pat. No. 4,701,425 shows an infrared and ultraviolet absorbing glass which is basically a soda-lime-silica glass and contains 0.29-0.6 wt % of iron expressed as Fe.sub.2 O.sub.3, 0.1-1.5 wt % of SnO.sub.2 and 0.1-1.6 wt % of TiO.sub.2. It is permitted that the glass contains up to 0.5 wt % of SO.sub.3. However, this glass is low in the absorption of ultraviolet rays and insufficient in the capability to absorb infrared radiation, and it is difficult to desirably temper this glass by a conventional method.